2007 triennial standards review

2007-2008 water quality standards rule revisions, Minn. R. chs. 7050 and 7053

This is an archival Web page from the 2007 – 2008 Triennial Revision of Minnesota Rules Chapter 7050 and the addition of a new rule, Minn. R. ch. 7053. This rulemaking also repealed Minn. R. parts 7056.0010 - 7056.0040, and Minn. R. parts 7065.0010 - 7065.0260.

Notice of Rule Adoption and USEPA Approval of Revised Standards:
MPCA noticed the adopted rule amendments in the Minnesota State Register on March 10, 2008 (32 SR 1699 – 32 SR 1728). The U. S. Environmental Protection Agency approved the rule amendments on May 23, 2008.

Timeline for the development of the acetochlor water quality standard: To understand how the Minnesota Pollution Control Agency (MPCA) developed the first-in-the-nation water quality standard for acetochlor, see a timeline of activities the MPCA underwent during the administrative process.

MPCA Citizens' Board Approves Adoption of Water Quality Rules: On December 18, 2007, the MPCA Board unanimously approved the adoption of the proposed rule amendments to Minn. R. ch. 7050, 7053, 7056, and 7065. Additional information regarding this Board action can be found at the Board Meeting Archives page. Several administrative steps remain before the Notice of Adopted Rules can be published in the State Register. Following the publication of this notice, the adopted rule and supporting documentation will be sent to the U.S. Environmental Protection Agency for their review and approval.

Post-Hearing Update: The rebuttal period on the proposed amendments to Minn. R. ch. 7050, the proposed adoption of Minn. R. ch. 7053, the proposed repeal of Minn. R. parts 7056.0010 - 7056.0040, and the proposed repeal of Minn. R. parts 7065.0010 - 7065.0260 closed on October 10, 2007. The entire rulemaking record has been filed with Administrative Law Judge Steve M. Mihalchick. Judge Mihalchick will issue a report on the proposed rules within approximately 30 days after the close of the hearing record. The following includes Minnesota Pollution Control Agency (MPCA) staff post-hearing written submissions and the Administrative Law Judge's Report.

UPDATE: Post Hearing Record Closes October 3, 2007. There will be no public hearing in St. Paul on September 13, 2007. (See the Public Hearing Schedule section below for additional information.)

The MPCA is revising Minnesota Rules chapter 7050. These rules contain water quality standards and other provisions that help protect surface and ground waters from pollution. The purpose of this Web page is to provide information about the standards and other provisions the MPCA plans to revise.

Major changes being proposed include the addition of eutrophication standards for lakes, extension of the 1 mg/L phosphorus effluent limit to new or expanding discharges above a certain size, addition of a fish tissue standard for mercury, and the addition of new standards for two herbicides, acetochlor and metolachlor. Also the MPCA plans to split Minn. R. ch. 7050 into two rules to make water quality rules easier to use and understand. The revised Minn. R. ch. 7050 will contain numeric and narrative water quality standards and related provisions. A new rule, Minn. R. ch. 7053, is created to contain effluent limits, wastewater treatment requirements and related provisions. Also, the MPCA proposes to move the relevant provisions of two rules, Minn. R. ch. 7056 and 7065, into Minn. R. ch. 7053, and repeal these two otherwise outdated and superfluous rules.

Notice of hearing - State Register July 23, 2007

MPCA noticed the proposed rule amendments in the Minnesota State Register on July 23, 2007 (32 SR 87 – 32 SR 217). Included is the entire text of the proposed amendments to Minn. R. ch. 7050 and the proposed new rule, Minn. R. ch. 7053. Due to a publishing oversight the actual Notice of Hearing (which provides the dates, times and locations of the public hearings, identifies the Administrative Law Judge that will preside over the public hearings, and provides information on submitting comments) did not appear in the July 23, 2007 edition of the State Register. This Notice of Hearing was published in the July 30, 2007 edition of the State Register (32 SR 250 - 32 SR 255). There are direct and indirect links to documents, including the Notice of Hearing, the proposed amendments to Minn. R. ch. 7050 and 7053, and the Statement of Need and Reasonableness (SONAR) noted below. These documents can also be accessed via the MPCA Public Notice Web page.

Proposed rule language changes

The proposed rules, Minn. R. ch. 7050 and Minn. R. ch. 7053 are available in the PDF files below. Proposed new language is underlined and proposed deleted language is in strike-out. The first two files are versions maintained by the MPCA and the second two files are the certified versions of the rules from the Office of the Legislative Revisor of Statutes. Only parts of Minn. R. ch. 7050 that include proposed changes are included in both the MPCA and Revisor’s PDF versions of this rule (the Revisor’s version of Minn. R. 7050.0470 is incorporated into the MPCA file). The entire proposed new rule, Minn. R. ch. 7053, is included in both versions.

The text in the Revisor’s version of proposed Minn. R. ch. 7053 is all underlined because the whole rule is new. However, most of the provisions in Minn. R. ch. 7053 are not new, and most are not proposed for change. Most provisions have only been moved from the existing Minn. R. ch. 7050 unchanged to the new rule. The public is advised to review the MPCA version of Minn. R. ch. 7053 to understand which portions are proposed for change in this rulemaking. If any discrepancy is found between the MPCA and Revisor’s versions of the rules (except for the underlining in Minn. R. ch. 7053), the Revisor’s versions should be assumed to be correct.

Statement of Need and Reasonableness

The MPCA is required by the Administrative Procedures Act (Minn. Stat. ch. 14) to prepare a Statement of Need and Reasonableness (SONAR) to support the proposed rule amendments. The SONAR describes the reasons and the scientific basis for the proposed changes. The SONAR also addresses all the statutory requirements associated with proposed administrative rules. Due to the scope of this rulemaking, the SONAR has been divided into three volumes or “Books,” which are available in separate PDF files.

The content of each Book is listed below.

SONAR Book 1

  1. Separation of Minn. R. ch. 7050 into two rules, Minn. R. ch. 7050 and 7053.
  2. Language changes needed to facilitate the splitting of Minn. R. ch. 7050.
  3. Language changes needed to clarify and consolidate the rules.
  4. Reformatting and housekeeping changes.
  5. Eight major or substantive proposed changes to language in Minn. R. ch. 7050.
  6. Repeal of Minn. R. ch. 7056 and 7065.

SONAR Book I also includes information under the following major headings relevant to the whole SONAR, most of which is not repeated in SONAR Books II and III:

  1. Introduction.
  2. Background information on use classifications and water quality standards.
  3. Notification of the public.
  4. Agency’s statutory authority.
  5. Originally planned amendments postponed.


  1. Numeric eutrophication standards for lakes, shallow lakes and reservoirs.
  2. Requirement for new or expanding dischargers to meet a 1 mg/L phosphorus effluent limit if they discharge more than 1,800 pounds of total phosphorus per year.


  1. Addition of fish tissue water quality standard for mercury.
  2. Adoption of standards for two herbicides, acetochlor and metolachlor.
  3. Update the human health-based water quality standards for benzene and naphthalene.
  4. Adopt an E. coli standard to replace the current fecal coliform standard for protection of swimming and other forms of water recreation.
  5. Change the default industrial use classification from 3B to 3C, which will relax Class 3 standards for chlorides and hardness for most waters.
  6. Changes related to use classifications: update the Class 2A (trout waters) and Class 1 (drinking water) listings; correct and improve the use class listings.
  7. Propose 12 use classification changes for 12 waterbodies, including new limited resource value water segments (Class 7 waters).

Approximately 325 exhibits pertinent to the proposed amendments are cited throughout the SONAR. The complete list of exhibits is attached at the end of each SONAR book. Many exhibits are available in PDF files; exhibits can be obtained upon request.

Current water quality rules

The two primary rules that contain water quality standards for Minnesota are Minn. R. ch. 7050 and 7052.

  • Chapter 7050. Standards for Protection of Waters of the State. This rule contains standards that apply state-wide to both surface and ground waters.
  • Chapter 7052. Lake Superior Basin Water Standards. This rule is known as the Great Lakes Initiative and it applies only to Lake Superior and surface waters in the Lake Superior basin. No changes are being proposed to this rule.

These and other rules that deal with aspects of water quality can be accessed on the Minnesota State Rules for Water page from this Web site.

Why revise water quality standards

The federal Clean Water Act requires all states to review and, where necessary, revise their water quality rules every three years. This revision will satisfy that requirement.

The importance of clean lakes to the state's economy and to our high quality of life in Minnesota hardly needs to be emphasized. Currently, Minnesota does not have numeric standards to protect lakes from the negative effects of excess nutrient loading. The adoption of eutrophication standards for lakes will help protect these valuable resources. Extension of the 1 mg/L phosphorus effluent limit to more dischargers will help protect both lakes and rivers from the effects of too much phosphorus.

Water quality standards should be updated periodically to reflect the latest scientific information. The MPCA is proposing to update selected standards and add new standards for two herbicides.

Major proposed changes

The major items proposed to be added or revised are outlined in this section.

A. Eutrophication (nutrient) standards for lakes

Many lakes in Minnesota show the harmful effects of excess nutrient loading from both point and nonpoint sources. Across the state as summer progresses into July and August, some lakes turn green with excess algae. Associated with algae blooms is a reduction in water clarity, possibility of floating mats of algae on the surface, and other undesirable effects, which make these lakes much less inviting for swimming or even fishing. In very severe cases, algae blooms can include species that are toxic to pets, wildlife and humans. Excess phosphorus is almost always the cause of these undesirable changes. “Eutrophication” is the term applied to this increase in biological productivity due to increased nutrient loading. “Cultural eutrophication” is the term used when the excess nutrients are a result of human activities.

Numeric standards. The MPCA is proposing numeric standards for phosphorus and two indicators of eutrophication that measure the response of lakes to excess phosphorus. The two indicators are chlorophyll-a (a green pigment that measures the abundance of algae), and Secchi disk transparency or Secchi depth (a measurement of water clarity). The standards will help protect lakes for recreational uses such as swimming and boating, a healthy aquatic community including game fish and aquatic plants, and the aesthetic enjoyment of lakes.

Because our lakes reflect the very diverse ecosystems in Minnesota, ranging from the forests in the north to the prairie and agricultural lands in the south, proposed lake standards will be different for different ecological regions of the state (called ecoregions). The ecoregion concept and the seven ecoregions in Minnesota are described in a Web page cited under “Links.” Ecoregion-based standards are proposed for the four ecoregions listed below that contain about 98 percent of all lakes in Minnesota.

  • Northern Lakes and Forests
  • North Central Hardwood Forest
  • Northern Glaciated Plains
  • Western Corn Belt Plains

Besides proposing different standards based on the ecoregion in which the lake is located, the MPCA is proposing separate sets of standards for the four categories of lakes listed below:

  • Lake trout lakes (lakes that support natural populations of lake trout),
  • Stream trout lakes (lakes managed for stream trout species),
  • Lakes and reservoirs with a maximum depth greater than 15 feet (deep lakes), and
  • Lakes with a maximum depth less than 15 feet (shallow lakes).

Proposed eutrophication standards by ecoregion and lake type

Ecoregion and lake type Total phosphorus Chlorophyll-a Secchi depth
Units µg/L

not less than

Northern Lakes and Forests
- Lake trout lakes
12 3 4.8
- Stream trout lakes
20 6 2.5
- Deep and shallow lakes
30 9 2.0
North Central Hardwood Forest
- Stream trout lakes
20 6 2.5
- Deep lakes 40 14 1.4
- Shallow lakes
60 20 1.0

Western Corn Belt Plains
Northern Glaciated Plains

- Deep lakes
65 22 0.9
- Shallow lakes
90 30 0.7

µg/L=micrograms per liter; ppb = parts per billion

Supplemental narrative standards. Even within an ecoregion and a lake type, lakes can vary greatly in size, depth, natural levels of nutrients, and many other characteristics. For this reason the proposed numeric standards will be supplemented by language in the rule that:

  • Protects lakes with water quality better than standards from being degraded.
  • Recognizes that some lakes will not meet standards due to natural causes.

It is important to expand on the first bullet. The MPCA wants to be very clear that the adoption of eutrophication standards does not mean that it is acceptable to degrade a high quality lake “down to” the level of the standards. The protection of Minnesota’s high quality lakes, that is, lakes with water quality better than the proposed standards, is extremely important. Such lakes typically have very great recreational and aesthetic value, as well as great economic value. An example will help illustrate what we mean. If a non-trout lake in the Northern Lakes and Forest ecoregion with very good water quality consistently has Secchi disk water clarity measurements in the 6 to 8 meter range (20 to 26 feet), MPCA policy is to maintain that good water clarity (and associated low in-lake phosphorus levels), and work to prevent a noticeable decline in water clarity to, for example, 4 to 6 meters (13 to 20 feet) even though 4 to 6 meters more than meets the proposed Secchi disk standard of 2 meters.

While it is very important to protect lakes that are better than standards, the MPCA also realizes that some lakes can never attain the proposed eutrophication standards. Lakes that can not meet the standards due to natural causes would not be considered to be “in violation” of the standards. Determination of whether the nutrient loading to a lake is natural or anthropogenic will be based on lake-specific monitoring data and other relevant information.

The MPCA is including a definition of “natural causes” in the proposed rule, which is:

“Natural causes” means the multiplicity of factors that determine the physical, chemical or biological conditions that would exist in a water body in the absence of measurable impacts from human activity or influence.

While the definition says “in the absence of human influence” the MPCA recognizes that the concept of “natural causes” must reflect certain realities of today’s world. We can not expect all lakes in Minnesota to exhibit the same water quality and trophic conditions they had 200 years ago. Population growth, urban and suburban expansion, land use changes such as row-crop agriculture, are essentially irreversible factors that can impact lake resources. The MPCA’s concept of “natural causes”, as it relates to the eutrophication standards, will account for some unavoidable changes in water quality and trophic status due to these “essentially irreversible” factors. However, the goal will be to achieve the best quality feasible in such lakes, following implementation of all applicable point source requirements, and implementation of all appropriate and reasonable best management practices throughout the lake’s watershed to minimize nonpoint sources of nutrients.

Additional narrative rule language associated with the numeric standards states that the proposed standards are to be compared to phosphorus, chlorophyll-a and Secchi depth data averaged over the summer growing season; and, that for the eutrophication standard to be exceeded, both the phosphorus (cause) and either the chlorophyll-a or Secchi depth (effects) standards should be exceeded. Also, standards for reservoirs can be developed on a case-by-case basis.

Use of Eutrophication Standards. How will these proposed standards help protect Minnesota’s lakes? Once adopted, implementation of the eutrophication standards will be important if they are to be effective in protecting lakes. The most effective way to implement the new standards, in our view, is through a combination of state and local governmental programs, both mandatory and voluntary that reduces nutrient loading to lakes, and by the use of the standards as an educational tool. Adopted numeric standards, as opposed to MPCA guidance, which is what we have now, will have greater legal authority, greater visibility and accessibility because they will be in legally adopted rules. This will enhance their use by other state agencies, consultants, local governments and lake associations. For example, having the standards in rules may support county commissioners and zoning officers in making decisions which will better protect lake resources. Also, the standards can serve as a benchmark to help lake associations assess the condition of “their” lake; and they can be used to reinforce educational efforts to help lake associations, lakeshore property owners and individual lake users make good decisions to protect lakes.

The proposed eutrophication standards may become the basis for setting a phosphorus effluent limit for some dischargers. The situations where this might occur are outlined below:

  1. Except possibly in a few unique cases, the proposed eutrophication standards will not become direct “end-of-pipe” limits.*
  2. The proposed standards could be the basis for an effluent limit more stringent than 1 mg/L if a new or expanding discharger would cause the phosphorus in a receiving lake (or downstream lake), to exceed the applicable eutrophication standards. In these situations, the limit would be lowered to the level necessary so the standards will be met in the downstream lake.
  3. If the new or expanded discharge would not cause an exceedance of the standard, the limit will be 1 mg/L, the same as current practice.
  4. If the receiving lake or downstream lake is already in violation of nutrient criteria, and is on the impaired waters (303(d)) list, federal Clean Water Act requirements form the basis for permitting existing, expanding or new discharges.** To comply with the federal requirements, the MPCA proposes to freeze the current mass loading of an existing discharger that wishes to expand.

*By “unique cases” we have in mind, for example, a proposed new discharge directly to a very high quality lake of special recreational value. It is very unlikely someone would propose such a discharge, and even more unlikely that it would pass existing nondegradation requirements and public opposition. In this highly unlikely scenario, the proposed phosphorus standard might be the proposed “end-of-pipe” limit.

**Code of Federal Regulations, 40 CFR 122.4(i) and 40 CFR 122.44(d)(1).

Additional Information. The lake Web pages listed under “Links” provide information on MPCA lake programs, including the volunteer lake monitoring program, and tips on how citizens can protect lake water quality. Also, through these Web pages the reader can find detailed information and links to documents describing the history, development and basis for ecoregion-based nutrient criteria, which are the precursors for the proposed numeric eutrophication standards.

The MPCA is finding that rivers and wetlands can be negatively impacted by excess nutrients as well. At this time the MPCA is proposing eutrophication standards only for lakes, but standards for rivers and wetlands may be proposed in the future. The U.S. Environmental Protection Agency (EPA) is requiring states to adopt nutrient standards for lakes and to gather data on the impacts of nutrients on rivers and wetlands.

B. Expanded application of 1 mg/L phosphorus effluent limit

To further protect lakes and rivers from the negative effects of excess nutrients, the MPCA is proposing that new or expanding dischargers must meet a 1 mg/L total phosphorus (TP) effluent limit after May 1, 2008, if they discharge more than 1,800 pounds of phosphorus per year (see PDF file, proposed Minn. R. 7053.0255). The current rule (Minn. R. 7050.0211, subp. 1a.) applies a 1 mg/L TP limit to dischargers if the discharge is directly to or affects a downstream lake or reservoir. This part of the existing rule will not change, but under this proposal, new or expanding facilities that discharge more than 1,800 pounds of phosphorus per year, will get a 1 mg/L limit without the need to demonstrate “affects.” Wisconsin in 1992 and Illinois in 2006 adopted similar phosphorus limit rules.

The proposal is consistent with the MPCA Phosphorus Strategy (Strategy) (see MPCA Lakes Web page). The Strategy was developed by MPCA staff to provide a consistent framework for implementing the current 1 mg/L TP limit and to promote reductions in phosphorus loading from point sources. The MPCA citizens Board approved the Strategy in March 2000. Since then between 35 and 40 new or expanding facilities have gotten 1 mg/L TP limits for a variety of reasons that might not have gotten them prior to implementing the Strategy. Thus, to a large extent, the proposed extension of the TP limit is already being implemented under the Strategy. The proposal will codify portions of the strategy in rule and sustain the gains made in reducing phosphorus loading from point sources. Also, TP limits for many dischargers are already being mandated or recommended in much of the state, due to:

  • The terms of existing rules (e.g., all dischargers in the Lake Superior basin);
  • The implementation plans of completed or pending large-scale nutrient-related TMDLs (e.g., Minnesota and Upper Mississippi Rivers); or
  • Nutrient reduction goals and basin plans (e.g., St. Croix basin).

The basis for the proposed de minimis loading of 1,800 pounds per year, below which the proposed 1 mg/L limit does not apply, is discussed in the Strategy documents. A wastewater treatment plant discharging 200,000 gallons per day at a typical effluent phosphorus concentration of 3 mg/L will discharge about 1,800 pounds in a year. This size plant is typical for a community with a population of about 2,000 people. The proposed de minimis cut-off will exclude more than half of all wastewater treatment facilities from the proposed extension of the TP limit, including most communities with stabilization pond treatment systems. The de minimis loading, however, does not apply to facilities that discharge directly to or affect a lake or reservoir. Such facilities of any size are subject to the 1 mg/L TP effluent limit as is the case now.

The MPCA is proposing rule language listing three situations that allow a discharger to demonstrate to the MPCA that the 1 mg/L limit should not apply to them. The proposed exemptions reflect comments from outside parties and the experience gained in implementing nutrient-related TMDLs.

An exemption may be appropriate if:

  1. The discharge is included as part of the implementation of a nutrient-related TMDL. In this case, if the TMDL is complete at the time the facility is in the planning stage, the TMDL will determine the TP limit.
  2. The environmental harm from meeting a limit outweighs the environmental benefits.
  3. The discharge is to a river in one of the following watersheds; a summer only limit is a possibility.
    1. Lower Mississippi River below Lake Pepin and its tributaries,
    2. Missouri River and its tributaries,
    3. Cedar and Des Moines Rivers and their tributaries in Minnesota, or
    4. The Bois de Sioux and Red Rivers and their tributaries.

Exemption “A” allows a discharger that is part of a nutrient-related TMDL to get the TP limit determined to be necessary by the TMDL if the facility is in a planning phase at the time the TMDL is final. If the TMDL has addressed nutrient issues and determines that a phosphorus limit is not needed, no limit will be imposed. If the TMDL is not complete at the time construction commences, or if the discharge is outside the scope of the TMDL, the 1 mg/L limit will be applicable to dischargers that exceed the de minimis loading.

Exemption “B” allows a discharger to petition for a higher limit or no limit if they can demonstrate that meeting the TP limit will cause more harm than good. This exemption is applicable to a broad range of situations where the environmental and economic cost of phosphorus removal clearly exceeds the gains.

Exemption “C” allows dischargers located in certain watersheds to petition for a suspension of phosphorus treatment in the winter if chemicals are used. The rationale behind this exemption is that, in spite of reports in the scientific literature of negative impacts of excess nutrients on rivers and streams, local data showing negative impacts in these watersheds, particularly in the winter, is limited.

Cities or industries that feel they qualify for one or more of the exemptions can submit information to the MPCA supporting their case. The MPCA will evaluate the information and decide whether or not to grant the request. The MPCA decision can be contested by any party through the permit issuance process.

C. Proposed new mercury standard

Mercury is one of the most prevalent and troublesome pollutants the MPCA deals with. Over 1,300 lakes and river segments in Minnesota for which we have data exceed mercury standards, as measured in resident fish, the water, or both. Almost all our mercury comes from atmospheric fallout, and most of that from sources outside the state. Because the primary source of mercury to people in Minnesota is the fish we eat, the MPCA is proposing to augment the current standard that defines a safe level in water with a standard that defines a safe level in fish tissue. “Safe” in this context means safe for sensitive populations (women of child-bearing age and children) that eat fresh water fish up to, but not exceeding, a frequency of one meal per week. The MPCA plans to retain both mercury standards currently in the rules; the statewide 6.9 ng/L standard and the 1.3 ng/L standard that applies in the Lake Superior basin.

The MPCA proposed standard of 0.2 mg/kg or parts per million (ppm) in edible fish tissue is based on a modification of the 2001 EPA mercury criterion of 0.3 ppm. The 0.2 ppm value is more stringent than the EPA criterion because the MPCA assumes Minnesotans eat more fresh water fish than EPA assumes people eat nation-wide (30 grams per day vs. 17.5 grams per day). Thirty grams per day equals about one meal per week. Also, 0.2 ppm mercury in fish is the trigger used by the Minnesota Department of Health (MDH) to advise women and children to eat fish no more than once per week every week all their life. Thus, the proposed standard is compatible with the MDH fish consumption advice. The MPCA has used the 0.2 ppm value to assess lakes and rivers for impairment due to mercury since 2002.

D. Update two human health-based standards

A water quality standard is “human health-based” (HH-based) when the concentration in water that is protective of people that eat fish (and in some cases use the same surface water for drinking) is lower than the concentration needed to protect fish and other aquatic organisms from the toxic properties of the chemical.

The MPCA plans to revise two HH-based standards, benzene and naphthalene, because EPA reviews of their effects on human health indicate that both are more toxic than thought in 1994 when the current standards were adopted. Benzene is a carcinogen and naphthalene is a noncarcinogen. The proposed new chronic standards will replace most of the existing standards, as shown in the following table.

Proposed Benzene and Naphthalene Chronic Standards Compared to Existing Standards

All units, µg/L Class 2A Class 2Bd Class 2B, C & D
Proposed standards
Benzene 5.4 6.0 98
Naphthalene 65 81 81
Existing standards
Benzene 9.7 11 114
Naphthalene 81 81 81

E. Addition of standards for acetochlor and metolachlor

The Minnesota Department of Agriculture (MDA) asked the MPCA to develop standards for several agricultural pesticides commonly used in Minnesota. The MPCA agreed to develop standards for two herbicides of greatest interest to MDA for which standards do not already exist. They are acetochlor and metolachlor. The EPA has not published an aquatic life criterion for either chemical; thus, the MPCA must develop the proposed standards “from scratch.”

Both acetochlor (example trade names: Surpass, Harness) and metolachlor (Bicep, Dual) are preemergence herbicides used to control annual grasses and some broadleaf weeds. Over three million pounds of acetochlor and two million pounds of metolachlor were sold in Minnesota in 2004 for use mainly on corn.

The MDA pesticide monitoring programs have found both herbicides in ground water and surface waters. MDA is recommending the implementation of voluntary best management practices to protect ground water from acetochlor and metolachlor and to protect surface waters from acetochlor.

The proposed standards for acetochlor and metolachlor are shown in the table below. The chronic standards are based on the toxicity of the two herbicides to aquatic plants. The acute toxicity-based standards, the Maximum Standard and Final Acute Value, are based on animal toxicity data.

Proposed Acetochlor and Metolachlor Standards

Proposed Class 2

µg/L (parts per billion)

µg/L (parts per billion)

Chronic (4-day mean)



Maximum (1-day mean)



Final Acute Value (1-day mean)



It is clear from the toxicity data for both herbicides that aquatic plants are more sensitive than fish and aquatic invertebrates. However, plant toxicity data is more difficult to interpret than the more traditional animal toxicity data, and EPA provides little guidance on how to use plant data. With this in mind the MPCA felt it was important to outline protection-level goals to be achieved by chronic standards based on plant data. These goals include:

  • Protect the overall integrity of the plant community from significant impacts. For example, avoid discernable or projected negative shifts in species composition, such as green algae species replaced by a blue-green algae, or a sensitive "desirable" macrophyte replaced by a "less desirable" macrophyte.
  • Protection of the most sensitive species tested from all impacts is not necessary, unless it is clear that it is ecologically important in Minnesota.
  • Target approximately a 20th percentile level of protection based on the body of chronic toxicity data for plants.

Two species commonly used in herbicide toxicity tests, a species of algae, Selenastrum capricornutum, and a duckweed, Lemna gibba, are very sensitive to both acetochlor and metolachlor. Chronic standards that would protect these two species from any impact at all times would need to be lower than the standards being proposed. Selenastrum is a very minor component in lake samples in Minnesota and is easily replaced by another genus of green algae, Scenedesmus. Lemna gibba does not occur in Minnesota; however, a related species of duckweed, L. minor, is very common. Data for metolachlor and other herbicides suggest that L. minor is not as sensitive as L. gibba. Therefore, neither of the two very sensitive species is considered to be "ecologically important" in Minnesota. The MPCA believes the proposed standards will protect the overall integrity of aquatic plant (and animal) communities, and are consistent with the goals listed above.

Both herbicides appear to be mobile in most soils and moderately persistent in the environment, but they apparently do not bioaccumulate in fish and wildlife. Human health-based standards were calculated for both herbicides and they are less stringent than the proposed plant toxicity-based chronic standards.

More detailed information on how the proposed chronic standards were developed from the plant data is provided in the following PDF file:

F. Replace the fecal coliform bacteriological standard with E. coli

Water contaminated with bacteria from human or animal fecal material can cause illness in humans if ingested. Bacteriological standards for surface waters are designed to protect swimmers from getting sick if they ingest small quantities of water. The EPA is urging all states to update their bacteriological standards. The MPCA is proposing to replace the current fecal coliform standard with an E. coli standard, based on an EPA criterion. MPCA’s goal is to adopt the E. coli standard with as little disruption as possible to ongoing programs, specifically to:

  1. Keep the protection level for swimmers the same.
  2. Keep the number of waters considered impaired for swimming about the same.
  3. Retain current assessment methods for determination of bacteriological impairment.
  4. Minimize impact on ongoing bacteriological total maximum daily load studies.
  5. Not impact the BEACH program on Lake Superior beaches.

The MPCA is recommending the E. coli standards shown in the table below. The current fecal coliform standard is included for comparison.

Proposed E. coli Standards Shown with the Current Fecal Coliform Standard for Class 2 and Class 7 Waters

Proposed E. coli Standards Shown with the Current Fecal Coliform Standard for Class 2 and Class 7 Waters

cfu = colony forming units
*126 E. coli cfu per 100 ml is the 30-day geometric mean EPA criterion (1986).

In order to understand the relationship between fecal coliform and E. coli levels in rivers, for several years the MPCA analyzed for both indicators from samples taken in the MPCA routine monitoring program. The analysis of these paired fecal coliform and E. coli measurements suggests that the recommended E. coli 30-day geometric mean standard may be slightly more stringent than the current fecal coliform standard. However, because of the variability in bacteriological data, the analysis does not support proposing a geometric mean standard different from the EPA criterion of 126 colony forming units (cfu) per 100 ml.

EPA allows some flexibility to states to determine the appropriate maximum standard. The MPCA is proposing a maximum standard of 1260 cfu/100 ml. Again, the analysis of the paired fecal coliform/E. coli data indicates this value may be slightly more stringent than the current maximum fecal coliform standard of 2000 cfu/100 ml, but within the variability of the data. The MPCA is proposing to do away with the more stringent 10 percent maximum standard currently applicable to trout waters (400 cfu/100 ml), and make the maximum standard the same for all waters (see table above). The MPCA believes that the more stringent standard for trout waters is not needed, and that swimmers in any category of Class 2 waters should receive the same level of protection.

The bacteriological standard applicable to limited resource value (Class 7) waters is designed to protect types of water recreation where emersion in the water is unlikely, such as wading and boating. The MPCA proposes to replace the current Class 7 standard with an E. coli standard that provides the same level of protection (see table above).

It is important to emphasize that the standards proposed for change are the ambient standards applicable to lakes, rivers and streams in Minnesota. The current fecal coliform effluent limit of 200 fecal coliform cfu/100 ml as a monthly mean that appears in discharge permits is not proposed for change (existing Minn. R. 7050.0211 / proposed Minn. R. 7053.0215).

G. Change the classification for industrial use protection for most waters from Class 3B to 3C

All surface waters in Minnesota are protected for industrial uses (Class 3A, 3B, 3C or 3D). Most waters are assigned the 3B subclass by “default” (Minn. R. 7050.0430). Class 3 standards are intended to protect industrial piping and equipment from scaling and corrosion when surface waters are used by industries. The Class 3 standards for chlorides and hardness are shown in the table below, along with the Class 2 chloride standard for comparison.

Standards for chlorides and hardness. The proposal is to change the classification of most waters from Class 3B to 3C.

Class 3 and Class 2 information

The Class 3B standards for chlorides and hardness are generally the most stringent standards for these substances applicable to waters of the state. They are problematic for a few dischargers, particularly in situations where the receiving water provides little or no dilution and where background concentrations are high. The MPCA has granted approximately six variances to dischargers for relief from these standards.

The MPCA is recommending a change to the “default” classification from 3B to 3C for most waters covered under the “unlisted waters” provision in Minn. R. 7050.0430 as well as certain waters “specifically listed” in Minn. R. 7050.0470. Currently, any water body that is not specifically listed in Minn. R. 7050.0470 is classified as 3B by “default”. The change to Class 3C will have the effect of making the chlorides and hardness standards applicable to most waters less stringent (see table above). All trout waters will remain Class 3B.

The MPCA believes this change can be made with little or no harm to the environment. The Class 1 (drinking water) and Class 2 (aquatic life) chloride standards are not being changed. The goal is to change what, in some locations and situations, are over-protective standards that have proven to be largely unnecessary. The purpose of the change is to reduce the need for variances that some dischargers must seek to gain relief from the Class 3B standards. However, the change will not eliminate the need to consider variances to chlorides and hardness in all situations. Variances to water quality standards must be processed on a case-by-case basis, costing the potential discharger, the MPCA and EPA time and money (EPA must approve variances).

H. Propose several new limited resource value waters

Limited resource value waters are surface waters able to support only a very limited aquatic community, and offer only very limited opportunities for water recreation. Most are headwater stream segments or channelized ditches that often have little or no flow in dry years. They range in length from less than a mile to 20 miles. The MPCA, with input from the Minnesota Department of Natural Resources, plans to propose the reclassification of 12 reaches to the limited resource category. The list of potential limited resource value waters shown below is based on requests from outside parties to have a specific reach assessed. These parties are usually a city or industry that either currently discharge or propose to discharge to the reach.

List of Potential Limited Resource Value Waters


Stream reach


Party requesting the reclassification


County Ditch No. 45 (Branch Lateral 3)


Golden Oval Eggs at Renville, MN


County Ditch No. 45


New outfall location for Southern Minnesota Beet Sugar Cooperative

3, 4

Lateral Judicial Ditch No. 29, Judicial Ditch No. 29


Evan, MN


Judicial Ditch No. 4

Lac Qui Parle

Lac Qui Parle Oil at Dawson, MN

6, 7

Unnamed Ditch to Sater’s Creek, and a portion of Sater’s Ck.


Agri-Energy at Luverne, MN


Unnamed Ditch to County Ditch No. 42


Winthrop, MN

9, 10, 11

Unnamed Ditch to Unnamed Ditch to Deer Creek (Co. Dt. 71)


Myrtle, MN


County Ditch 11


Manchester, MN

The MPCA is proposing to re-classify, back to Class 2, a portion of the downstream reach of Renville Co. Ditch No. 45 that is currently classified as a limited resource value water.

An unnamed creek to Cedar Creek at Isanti Estates, Isanti County, was assessed but MPCA staff recommend that it retain its current Class 2B classification.

I. Other changes

Listed below are other changes to Minn. Rules ch. 7050 the MPCA is proposing. Some are substantive but relatively minor. Others are minor and non-substantive, such as changes that will clarify existing rule language or make the rules easier for the public to use. None is likely to have any significant environmental or economic impact.

  • Split Minn. R. ch. 7050 into two rules to make it easier to read and understand. The revised Minn. R. ch. 7050 will contain the beneficial use classifications, numeric and narrative water quality standards, nondegradation and other provisions related to ambient standards.
  • A new Minn. R. ch. 7053 will contain existing wastewater treatment requirements, effluent limitations, aquaculture, feedlot and related provisions.
  • Changes to rule language required to facilitate the splitting of Minn. R. ch. 7050 into two rules, and changes to clarify, consolidate and update language to make the rules easier to understand, without changing the meaning of the rule.
  • Add definitions for nine terms.
  • Improve the introductory policy statement for nondegradation to all waters.
  • Extend the time period for the review of variances to effluent limits from 3 to 5 years.
  • Remove the provision that municipal discharges, which have advanced wastewater treatment requirements, must meet a 5 mg/L total suspended solids limit if they have failed to implement a pretreatment program.
  • Update the EPA drinking water standards, correct errors associated with exemptions to the drinking water standards as they apply to raw water supplies, and remove the Class 1D provisions.
  • Reword provisions allowing the site-specific modification of standards so that standards for any use class can be modified, not just Class 2 standards.
  • Propose a minimum hardness value of 10 mg/L for determination of hardness-related metal standards.
  • Move pertinent provisions in Minn. R. ch. 7056 and 7065 to the new Minn. R. ch. 7053 and repeal the former two outdated rules.
  • Update the list of trout waters listed in Minn. R. 7050.0470 to reflect the most recent list of waters designated as trout streams or trout lakes from the Minnesota Department of Natural Resources.
  • Addition of lake identification numbers to listed lakes and corrections to certain legal descriptions in Minn. R. 7050.0470.

Benefits and costs

The MPCA is required by law to consider the benefits and the costs to cities, industries, farmers, other governmental agencies and any affected party of the proposed rule amendments.

The MPCA believes the proposed rulemaking will benefit the environment and the citizens of Minnesota. In general it is difficult to quantify in dollars estimated benefits. An exception is the value of lakes to Minnesota’s economy and to lakeshore property values, which can be quantified through several means. Aspects of the proposed rulemaking will mean added costs to some parties, mostly point source discharges that have discharge permits. The MPCA has estimated these potential costs.

Minnesota’s water resources are the cornerstone of a $10 billion a year tourism industry. Also, the contribution clean lakes and rivers make to the high quality of life in Minnesota can not be overstated. The proposed eutrophication standards for lakes and the extension of the phosphorus effluent limit will help protect these resources from excess nutrients.

Several of the proposed amendments have the potential to save dischargers and other parties money. These are the proposed reclassifications of about 12 short headwater (channelized) stream reaches to limited resource value waters, allowing site-specific modifications of standards for any beneficial use class, and the simplification and clarification of the water quality rules.

The extension of phosphorus effluent limits to new and expanding discharges is the proposed change with the largest cost implications. The MPCA has estimated treatment costs that may be incurred by new or expanding municipal and industrial wastewater treatment plants with a discharge larger than 200,000 gallons per day. Using conservative assumptions, the estimated total capital cost for 35 municipal facilities projected to be impacted over the next five years is $61 million (average of high and low estimates). The estimated potential capital costs to seven categories of industries that may get phosphorus limits due to the proposal is $4.27 million (estimated costs for two of the seven categories is zero). However, most of these costs cannot be attributed to the proposed rule change for a number of reasons outlined in the Statement of Need and Reasonableness (SONAR).

The proposed eutrophication standards may result in some dischargers getting phosphorus limits more stringent than 1 mg/L. The MPCA predicts that over the next five years roughly 15 dischargers may be required to remove phosphorus to a level below 1 mg/L at an estimated total capital cost of $8.2 million.

The proposed change to the default industrial use classification will relax the applicable chloride and hardness standards for most surface waters. This may have cost consequences for some municipalities and industries if the chloride and hardness concentrations in source waters (used for drinking or industrial use) increase, which is not expected to happen.

A potential cost to the MPCA and some outside entities is the possible need to monitor for both fecal coliform and E. coli during a transition period from one standard to the other.

The proposed acetochlor and metolachlor standards may result in added costs to some farmers and the pesticide registrants. Costs to farmers may be the result of having to use an alternative herbicide in impacted watersheds, or the need to implement best management practices to control nonpoint source runoff.

Public hearing schedule

The MPCA will hold public hearings as shown below. Be aware that access to the MPCA St. Paul Office is controlled; to attend a hearing you will be asked to sign in at the security desk and provide photo identification such as Minnesota driver’s license.

  • MPCA-St. Paul, Board Room, 520 Lafayette Road North, St. Paul, Minnesota 55155.
    • Wednesday, August 29, 2007, beginning at 1:00 p.m. and continuing until all parties are heard. The hearing will resume at 6:30 p.m.
    • Thursday, August 30, 2007: MPCA-St. Paul, beginning at 9:30 a.m. and continuing until all parties are heard.
  • MPCA-Duluth, 525 Lake Avenue South, Suite 400, Duluth, Minnesota 55802.
    • Tuesday, September 4, 2007, beginning at 1:30 p.m. and continuing until all parties are heard. The hearing will resume at 6:30 p.m.
  • MPCA-Brainerd, 7678 College Road, Suite 105, Baxter, Minnesota 56425.
    • Wednesday, September 5, 2007, beginning at 1:30 p.m. and continuing until all parties are heard. The hearing will resume at 6:30 p.m..
  • MPCA-Detroit Lakes, 714 Lake Avenue, Suite 220, Detroit Lakes, Minnesota 56501.
    • Thursday, September 6, 2007, beginning at 1:00 p.m. and continuing until all parties are heard.
  • MPCA-Marshall, 1420 East College Drive, Suite 900, Marshall, Minnesota 56528.
    • Tuesday, September 11, 2007, beginning at 6:30 p.m.